Liquid crystal projectors employ a liquid crystal display panel positionable between a projector lamp and a lens. An illumination beam from the lamp passes through the liquid crystal display panel to form an image beam. The image beam is enlarged by a projection lens system and focused to cast an enlarged picture on a display screen.
To provide maximum contrast of the displayed image, liquid crystal display panels must be maintained at a cool and uniform temperature. The exposure of the display panel to heat from the projection lamp substantially degrades the quality of the projected image.
A prior projector employing a liquid crystal display panel is disclosed in U.S. Pat. No. 4,875,064 to Umeda. In the Umeda projector, the illumination beam passes through ultraviolet reflectors and absorbers to remove thermal energy from the beam. A reflective mirror redirects the illumination beam so that the beam is perpendicular to the lamp. A condenser lens directs the illumination beam to the liquid crystal display panel. The display panel forms an image beam which passes through a fresnel lens, and is redirected by a mirror. The image beam then passes through a projection lens, off a projection mirror, and on to a projection screen. While the Umeda device provides a relatively compact projector and employs ultraviolet reflectors and absorbers, the liquid crystal display panel is located in the same thermal environment as the illumination source, and is therefore subject to substantial heat and temperature fluctuations which degrade the quality of the image and contribute to premature failure of the panel.
A need exists for a liquid crystal display panel projector which provides a cool, thermally stable environment for the display panel. There is also a need for a compact projector having a reduced volume to permit integration with control equipment.